This invention relates to a compressor and more specifically to a gas flow system for a semi-hermetic compressor wherein the electric motor which is employed for driving the compressor may be cooled by refrigerant which is supplied to the suction side of the compressor.
Semi-hermetic compressors tend to be relatively large compressors which are used in large refrigeration systems. In the construction of such semi-hermetic compressors, it is desired to provide a cooling arrangement for cooling the electric motor which drives the crankshaft of the compressor to prevent overheating of the motor and, furthermore, to permit the electric motor to operate efficiently. Prior art arrangements which have been used to cool compressor electric driving motors have generally routed the suction refrigerant gas which flows into the compressor from the evaporator coil, past the end turn windings of the motor stator, through the motor rotor and over the laminations of the stator prior to conducting this gas to the suction inlet of the compressor cylinders. Thus, the physical arrangement for achieving such refrigerant gas flow has generally been to provide a suction inlet in the rear portion of the motor casing, to conduct the refrigerant gas in multiple parallel paths over the stator and rotor, to collect the gas after it has performed its electric motor cooling function and to then conduct the gas to the compressor cylinder suction inlet.
Such a gas flow arrangement is shown in U.S. Pat. No. 4,332,144 wherein a suction inlet is provided at one end of the motor housing so that the refrigerant gas flows through the suction inlet and over the electric motor prior to flowing to the compressor cylinder suction inlet. This prior art arrangement has several disadvantages. First of all, since the suction inlet of a compressor generally comprises a muffler chamber including a screen and a valve, the suction inlet is generally relatively massive and is constructed of cast iron or the like. Therefore, in such prior art gas flow arrangements, the electric motor housing must be relatively strong and massive to support the massive suction inlet which adds bulk and weight to the compressor and is, of course, undesirable. Furthermore, to provide such a massive and heavy motor casing also adds undesirable cost to the construction of such prior art compressors.
Another serious disadvantage of such a prior art electric motor cooling arrangement of a compressor is that the compressor does not readily lend itself to conversion to an alternately driven type of compressor such as a direct drive compressor which is driven with a conventional, self-contained electric motor, or a compressor which is driven by means of a belt and pulley arrangement. Thus, the construction of prior art semi-hermetic compressors has not lent itself to flexibility of crankcase design whereby the crankcase may be used to construct other types of compressors. It is therefore desired to provide a semi-hermetic compressor with a gas flow arrangement whereby the compressor crankcase may be used in compressors which are driven from an alternate source of power.
In one prior art arrangement disclosed in U.S. Pat. No. 2,180,493, a compressor is shown wherein the suction inlet is provided on the crankcase and wherein cooling of the motor is primarily accomplished by a water jacket. Furthermore, in this compressor, a small portion of the suction gas is drawn through and around the motor windings by means of fan blades constructed on an end ring of the rotor of the electric motor. However, in this arrangement, only a small portion of the inflowing suction gas is caused to flow around the motor windings, thereby contributing but little to the cooling of the electric motor. Additionally, there is no flow of gas through the electric motor so that the gas cooling arrangement is relatively inefficient. Furthermore, the use of a water jacket is undesirable as it requires plumbing connections to a source of supply for the coolant water, thereby increasing the cost of the compressor and its installation in a refrigeration system.
Still other prior art compressor arrangements have been provided wherein the electric motor is cooled by inflowing suction gas but wherein a unitary housing is provided for the motor and compressor so that the compressor does not lend itself to conversion to a compressor which is driven from an alternate source of power. Thus, it is desired to provide a compressor wherein the refrigerant suction inlet is mounted on the compressor crankcase and wherein the compressor may be converted to a compressor which is driven from an alternate source of power.